1. Field of Invention
This invention relates, in part, to draft gears used on rail cars to absorb shock during coupling and other physical impacts between the rail cars. Such draft gears are illustrated by U.S. Pat. No. 3,227,288 which issued on Jan. 4, 1966 to Mulcahy. More particularly, the present invention relates to improvements in the compression spring components of these draft gears. Such spring components are normally formed of an elastomer pad which is joined or bonded to a metal plate. Illustrative of the related prior art spring units are those illustrated in U.S. Pat. No. 4,198,037 which issued to David 0. Anderson on Apr. 15, 1980. The overall shock absorbing capacity of those spring units are affected, not only by the elastomeric pad design, but by the surface contact and bonding of the pad to the metal plates.
2. Related Art
Several alternative metal plate and elastomeric pad designs are depicted in the Anderson U.S. Pat. No. 4,198,037 identified above. Such combination designs are generally reflected in FIGS. 4 through 11. Each includes a surface incongruity in the metal plate which is intended to capture a portion of the elastomer that is forced into the incongruity by cold forming, i.e., the direct application of pressure which causes the elastomer to flow into the incongruities. The use and selection of any particular design is dependent upon the energy to be absorbed and the intended application for the spring. In large part, the design of FIGS. 5-7 of this prior Anderson patent has been the primary design used commercially by Anderson's assignee, Miner Enterprises, Inc., in its draft gears.
Another related prior patent is U.S. Pat. No. 4,566,678 which also issued to Miner Enterprises, Inc., on an application of David O. Anderson. This patent is similarly directed to an elastomeric pad formed of a thermoplastic Hytrel.RTM. that was joined to metal plates and intended to be used in a rail car buffer unit as well as other shock absorbing applications.